PHinisheD—“A discussion and support group for people trying to finish their dissertations or theses, and those who have been there.”
Discussion forums, helpful links, and an extensive list of books that other scholarly writers have found useful.

Association for Support of Graduate Students
“ASGS is a service organization for graduate students to help students plan, initiate and complete their theses or dissertations, produce the highest quality research, write effectively in the proper editorial style, obtain their academic degree(s), and improve their lives throughout the process.”
Not as extensive as PHinished, but still has a lot to offer.

Destination Dissertation by Sonja K. Foss. From the publisher’s comment: “Dissertations aren’t walls to scale or battles to fight; they’re destinations along the path to a professional career.”

There’s a veritable galaxy of resources for people who want to overcome resistance to writing; here are the three that have helped me the most.

Playing Ball on Running Water: Living Morita Psychotherapy David K. Reynolds, Ph.D.
Morita was a contemporary of Freud who believed that healing and growth result from deliberate, conscious action instead of from self-analysis. My copy is well-loved and heavily underlined; one passage affected me so strongly that I copied it out in the front of the book:

Jumping into reality, acting as the moment requires, eliminates some of the unnecessary suffering that accompanies procrastination and wishing that life were otherwise. Involvement in the doing not only moves us toward achievement of the immediate project, but it also distracts our attention from the foolish and unnecessary habit of focusing on our miserably bad luck.

Procrastination: Why You Do It/What to Do About It
Jane B. Burka, Ph.D., and Lenora M. Yuen, Ph.D.
Although I agree that it's more important to start acting than to understand what's fueling the resistance, I also know that understanding procrastination can make it easier to overcome. This time I not only underlined throughout, but copied out three passages:

Remember that an excuse is a red flag. It means that you’re at a choice point: you can procrastinate or you can act. Ask yourself, “Do I want to procrastinate right now? Is procrastination in my best interests right now?”

Experience confirms what research has shown: punishment is not a motivator.

It’s also better, in the long run, to stick to your limits because you’re honoring an agreement you made with yourself. Doing exactly what you said you would do—no more and no less—builds trust and confidence in yourself. These are valuable feelings that many procrastinators have lost.

Write or Die Websitehttp://lab.drwicked.com/writeordie.html
Whoever "Dr. Wicked" is, he’s brilliant. On his website, you have to keep writing to avoid varying kinds of consequences. You begin by choosing either a word-number goal (e.g., 500 words) or a time goal (e.g., 10 minutes). Next, you specify how long the grace period will be before the consequences start kicking in—Forgiving, Strict, or Evil. Finally, you choose your consequence mode (i.e., the level of severity): Gentle, Normal, or Kamikaze. In the latter, when your grace period is up, the program begins deleting what you’ve written, word by word.